Inductor arrangement for induction heating



I I illl April 1958 G. M. MUCHA 2,832,876

INDUCTOR ARRANGEMENT FOR INDUCTION HEATING Filed June 2, 1955 w ll a III'III INVENTOR Fig. 3 Fig. 4 GEORGE M. MUCHA BY I ATTORNEY United States Patent INDUCTOR ARRANGEMENT FOR INDUCTION HEATING George M. Mucha, Cleveland, Ohio, assignor to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Application June 2', 1955, Serial No. 512,732

4 Claims. (Cl. 219-10.79)

This invention pertains to the art of induction heating and more particularly to 'an inductor arrangement having magnetically permeable material as a part thereof.

The invention is particularly adaptable to inductor arrangements used in high frequency induction heating and will be described with particular reference thereto, although it will be appreciated that the frequency of the power is unimportant insofar as the invention is concerned.

In the art of high frequency induction heating, it is conventional to provide an elongated electrically conductive member which is placed in close spaced relationship to a metallic workpiece to be heated. High frequency currents flowing in this member generate a high frequency magnetic flux field which threads into the surface of the workpiece and induces high frequency currents to flow in the surface of the workpiece. To increase the concentration of the magnetic flux, it has been conventional to place magnetically permeable material in the form of a stack of magnetic laminations about the sides of the conductive member other than the workpiece facing surface. These laminations tend to heat, due to the high concentration of magnetic flux, and in order to cool them it has been conventional to soft solder or braze them to the electrically conductive member which is itself water cooled.

Difficulty has been experienced in the past with such arrangements due to warpage of the conductive member, either while in use or in storage. Such warpage is particularly detrimental because it makes accurate spacing of the conductive member relative to the workpiece difficult.

As a result of the present invention, it is believed that this warpage is caused by a differential expansion of the conductive member and the laminations. This differential expansion may be caused by corrosion between the laminations or capillary action causing fluids to enter between the laminations and elongating the stack, or due to different thermal coefiicients of expansion.

The present invention contemplates a laminated inductor arrangement of the general type referred to which overcomes all of the difficulties above set forth and others, and is simple in construction and has excellent electrical characteristics.

In accordance with the present invention, an inductor arrangement is provided comprising in combination an electrically conductive member and a stack of magnetically permeable laminations extending along the length of such member, and so arranged that the stack may expand and contract independently of the member.

Thus in one aspect of the invention the stack of laminations is held in assembled relationship by a frame so arranged as to maintain the stack in tight assembled relationship on the conductive member while permitting relative expansion and contraction of the stack, and also so arranged as to enable the laminations to be cooled.

The principal object of the invention is the provision of a new and improved inductor arrangement having ice magnetic laminations which will not warp in use or in storage.

Another object of the invention is the provision of a new and improved inductor arrangement wherein the laminations are free of the inducing member and yet may be artificially cooled.

Another object of the invention is the provision of a new and improved arrangement for mounting laminations on a high frequency inductor.

Still another object of the invention is the provision of a new and improved inductor arrangement having laminations which can expand and contract free of the conductive members of the inductor.

T he invention may take physical form in a number of different appearing parts and arrangements of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawing, which is a part hereof and wherein:

Figure 1 is a side elevational view of an inductor arrangement embodying the present invention;

Figure 2 is a cross-sectional view of Figure 1 taken approximately on the line 22 thereof;

Figure 3 is a cross-sectional view of Figure 1 taken approximately on the line 3-3 thereof; and,

Figure 4 is a cross-sectional view of Figure 1 taken approximately on the line 44 thereof.

Referring now to the drawing wherein the showings are for the purposes of illustrating a preferred embodiment of the invention only and not for the purposes of limiting same, the figures show a high frequency inductor arrangement of the type normally employed for heating an elongated narrow portion of a metallic workpiece and include an elongated electrically conductive member 10 which forms the main heating leg of the inductor, a pair of end conductor members 11-12 fastened to the ends of the member iii and extending upwardly therefrom for a short distance, and a pair of return conductor members 13-14 extending toward each other from the end members 11-12 respectively and terminating just short of each other to form a split 15. Fish tail leads 16-17 extend upwardly from the members 1314 respectively on each side of the split, to connect to an electrical power source not shown, such fish tail leads 1617 being conventional in the art.

Thus in the embodiment shown the side plates 32 are each formed in two pieces which overlap as at 38. The overlapping portions are provided with horizontally elongated openings 39 through which the center bolt 35 extends, whereby the two portions of the side plate 32 may be moved horizontally relative to each other.

The frame serves the function of holding the stack of laminations 28 both in assembled relationship and in position on the member If so that the lower surface 25 of the laminations 25 will be flush with the workpiece facing surface 20. Obviously, the exact relationship of the laminations to the member it) is not important. The showing is directed to the optimum way in which such laminations are employed in the art.

The frame 26 may be fixed to any part of the inductor. In the embodiments shown, however, the end plate 30 is brazed to the member 10. The member 31 is free to slide along the member It) so that the stack of laminations 25 and its supporting frame can expand or contract relative to the member 10 without creating any stresses or strain therein. In effect, it will be noted that the lamination and its supporting frame are rigidly fixed relative to the inductor at one point only.

Obviously, the frame 26 can be made extendable or contract-able in its length by any other known arrangement than the specific one shown. The frame 26 may be artificially cooled in manners which are known in the art.

The present invention has proven to be extremely practical in practice and has eliminated the problems of warpage of the inductors of the prior art which occurred both during storage and during use. The invention is not limited to the specific type of inductor shown. Its prime advantage, however, is in the form of inductor wherein the heating or main inducing member is generally elongated and straight substantially as shown in the figures.

Obviously, modifications and alterations differing in appearance from the embodiments shown will occur to others upon the reading and understanding of this specification, and it is my intention to include all such modifications and alterations insofar as they come within the scope of the appended claims.

" Having thus described my invention, I claim:

1. An inductor for use in induction heating comprised of an elongated main inducing member and a stack of extendable and contractable magnetic laminations extending along said member, said laminations being fixed to said member at one point only in the length of said stack to permit said stack to extend and contract relative to said member.

2. An inductor for induction heating, a combination of an electrically conductive elongated main heating memher, a stack of extendable and contractable magnetic laminations in operative and movable relationship with said member, and means fixing said stack of laminations relative to said member at one point only along the length of said stack to permit said stack to extend and contract relative to said member.

3. An inductor arrangement for induction heating comprising in combination an inductor including a main heating member, a stack of extendable'and contractable magnetic laminations about said member and slidable relative to the length thereof, a frame for holding said laminations in assembled relationship, said frame being fixed to said inductor at one point only to permit said stack to extend and contract relative to said member.

References Cited in the file of this patent UNITED STATES PATENTS 2,672,544 Finchelstein Mar. 16, 1954 

